How is the snowpack doing?

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The short answer:  not too good.  Something that is surprising in a La Nina year, when snowpacks should be above normal.

Take a look at the latest snow water equivalent map for the west (this is the amount of water in the snowpack compared to normal). The Cascades are near normal due to the considerable fall received last month--but that snow is aging fast.  Oregon and Idaho:  well below normal.  California's Sierra's are roughly 25% of normal.  You want snow?--head to Arizona and New Mexico, where some locations are nearly 300% of normal.  This is due to the frequent troughs and cut-off lows that have moved into that region due to the persistent high pressure over the eastern Pacific.

 Talking of persistent---current models suggest the east Pacific ridging will remain in place at least for the next week--although with weaker amplitude.  This will allow occasional weak fronts to move through--such as the system expected tonight and Sunday morning.  Here is the latest 6-10 forecast from the National Weather Service's Climate Prediction Center---dry over the west.  With such east Pacific ridging, a lot of our moisture is going into Alaska, where they are getting hammered.

Here is the upper level chart for Christmas Eve.  The ridge is so large and high amplitude, Santa will be blown way up into Alaska.  Favorable conditions for dropping down a chimney---nice and dry.

 Talking of snow conditions, the frequent periods of clearing over the mountains have led to frequent deposits of hoarfrost (see picture below).  The is important because when snow does return, such frost  result in an underlying weak layer that could lead to avalanches.  But we can worry about that later.

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